Gaming machines currently exist with bonus rounds in which a player has one or more opportunities to choose masked bonus awards from a group of symbols arranged in a pattern and displayed to the player. When the player chooses a masked symbol from the pattern, the bonus round removes the mask and either displays a bonus value or a bonus round terminator which terminates the bonus round. The controller of the gaming machine randomly places a predetermined number of bonus round awards and bonus terminators in the pattern at the beginning of the bonus round and maintains the positioning until the bonus round terminates. The outcome depends upon whether the player selects an award or terminator.
European Patent Application No. EP 0 945 837 A2 which is assigned on its face to WMS Gaming, Inc. discloses a bonus round of this type. In this type of round, each time the player enters the bonus round, the player has the same diminishing chance to select an award instead of a terminator. For example, that application discloses a bonus round that has 30 possible selections, 24 bonus awards and 6 bonus round terminators. Each time the player enters the bonus round, the player has a 100% chance of having a first pick, an 80% chance of having a second pick, a 63% chance of having a third pick, a 50% chance of having a fourth pick and so on.
It should be appreciated that once a bonus round of the type described above begins, the game will not change or alter the values of the masked awards. Once the game displays the masked awards, the game sets the values and positions for each award and does not alter either during the round. Therefore, the implementor of the above type of bonus round has one opportunity to generate or distribute awards having relatively high and low values.
For example, the application discloses a bonus round that has one 20 credit award, two 15 credit awards, two 10 credit awards, eight 5 credit awards, two 4 credit awards, three 3 credit awards, four 2 credit awards and two 1 credit awards. As the player advances through this type of bonus round, the probability of the player receiving an award having a particular value, e.g., an award having a high value, only increases slightly due to the lessening of remaining selections. Likewise, as discussed above, the probability of the player obtaining a bonus terminator increases by the lessening of remaining selections.
Because the above bonus scheme has only one opportunity to generate a set of values and because the probability of selecting a particular award or a bonus terminator only increases due to the lessening of remaining selections, bonus rounds of this type have no effective ability to alter their return/risk ratio so that players will receive higher bonuses as they advance farther and farther through the bonus round. For example, in the distribution stated above, the player has a 1 in 30 or 3.33% chance of selecting the 20 credit award in the player's first selection, a 1 in 29 or 3.45% chance in the second selection, a 3.57% chance in the third selection and a 3.70% chance in the fourth selection. The player has roughly the same probability in each selection to choose the high value award.
Increasing the number of high value awards does not solve the problem. If the above example included five 20 credit awards instead of just one, the probability distribution would change to 16.7% (5 in 30), 17.2% (5 in 29), 17.9% (5 in 28) and 18.5% (5 in 27), respectively. It should be appreciated that decreasing the total number of selections has roughly the same effect as increasing the number of high value awards. Thus, in the above type of gaming device, the player has roughly the same chance of choosing a high value award in the first pick as in the second, roughly double the chance of choosing a high value award in the first two selections as in the third selection, roughly three times the chance of choosing a high value award in the first three selections as in the fourth selection and so on.
Likewise, the above type of gaming device has no effective way to increase risk from one selection to the next. There is a 6 in 30 or 20% chance of terminating the round on the first selection, a 20.7% chance of terminating on the second selection, a 21.4% of terminating on the third, a 22.2% of terminating on the fourth and so on. The above type of gaming device cannot effectively alter return, risk or return/risk.
It should be appreciated that varying award returns and risk of bonus round termination increases player excitement and enjoyment. Players enjoy playing for high bonus awards or high return rounds. Gaming devices preferably present a risk of termination that is commensurate with the likelihood or rewarding a high return, and players enjoy playing high risk, high return games. Players also enjoy playing a game that lasts an extended period of time and provides a plurality of awards. Thus, it is desirable to have a bonus round of a gaming device that provides initial selections that are relatively low return/low risk and later selections having increasingly higher returns and higher risk.